Naturally occurring praseodymium (59Pr) is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr, with a half-life of 13.57 days and 142Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than six hours and the majority of these have half-lives that are less than 33 seconds. This element also has 15 meta states with the most stable being 138mPr (t1/2 2.12 hours), 142mPr (t1/2 14.6 minutes) and 134mPr (t1/2 11 minutes).
The isotopes of praseodymium range in atomic weight from 120.955 u (121Pr) to 158.955 u (159Pr). The primary decay mode before the stable isotope, 141Pr, is electron capture and the mode after is beta decay. The primary decay products before 141Pr are element 58 (cerium) isotopes and the primary products after are element 60 (neodymium) isotopes.
|-id=Praseodymium-121| 121Pr| style="text-align:right" | 59| style="text-align:right" | 62| 120.95539(54)#| 12(5) ms| p| 120Ce| (3/2)(+#)| |-id=Praseodymium-124| rowspan=2|124Pr| rowspan=2 style="text-align:right" | 59| rowspan=2 style="text-align:right" | 65| rowspan=2|123.94294(43)#| rowspan=2|1.2(2) s| β+| 124Ce| rowspan=2|| rowspan=2||-| β+, p (?%)| 123La|-id=Praseodymium-125| 125Pr| style="text-align:right" | 59| style="text-align:right" | 66| 124.93766(32)#| 3.3(7) s| β+| 125Ce| 3/2+#| |-id=Praseodymium-126| rowspan=2|126Pr| rowspan=2 style="text-align:right" | 59| rowspan=2 style="text-align:right" | 67| rowspan=2|125.93524(21)#| rowspan=2|3.12(18) s| β+| 126Ce| rowspan=2|(4, 5)| rowspan=2||-| β+, p (?%)| 125La|-id=Praseodymium-127| 127Pr| style="text-align:right" | 59| style="text-align:right" | 68| 126.93071(21)#| 4.2(3) s| β+| 127Ce| 3/2+#||-id=Praseodymium-127m| style="text-indent:1em" | 127mPr| colspan="3" style="text-indent:2em" | 600(200)# keV| 2# μs||| (11/2−)||-id=Praseodymium-128| rowspan=2|128Pr| rowspan=2 style="text-align:right" | 59| rowspan=2 style="text-align:right" | 69| rowspan=2|127.928791(32)| rowspan=2|2.85(9) s| β+| 128Ce| rowspan=2|(3+)| rowspan=2||-| β+, p (?%)| 127La|-id=Praseodymium-129| 129Pr| style="text-align:right" | 59| style="text-align:right" | 70| 128.925095(32)| 30(4) s| β+| 129Ce| (3/2+)||-id=Praseodymium-129m| style="text-indent:1em" | 129mPr| colspan="3" style="text-indent:2em" | 382.57(24) keV| 26(11)# μs| IT| 129Pr| (11/2−)||-id=Praseodymium-130| 130Pr| style="text-align:right" | 59| style="text-align:right" | 71| 129.923590(69)| 40.0(4) s| β+| 130Ce| (6, 7)(+#)||-id=Praseodymium-130m| style="text-indent:1em" | 130mPr| colspan="3" style="text-indent:2em" | 100(100)# keV| 10# s||| 2+#||-id=Praseodymium-131| 131Pr| style="text-align:right" | 59| style="text-align:right" | 72| 130.920235(50)| 1.50(3) min| β+| 131Ce| (3/2+)||-id=Praseodymium-131m| rowspan=2 style="text-indent:1em" | 131mPr| rowspan=2 colspan="3" style="text-indent:2em" | 152.4(3) keV| rowspan=2|5.73(20) s| IT (96.4%)| 131Pr| rowspan=2|(11/2−)| rowspan=2||-| β+ (3.6%)| 131Ce|-id=Praseodymium-132| 132Pr| style="text-align:right" | 59| style="text-align:right" | 73| 131.919240(31)| 1.49(11) min| β+| 132Ce| (2+)||-id=Praseodymium-132m1| style="text-indent:1em" | 132m1Pr[1] | colspan="3" style="text-indent:2em" | 30(30)# keV| 1# s| | | (5+)||-id=Praseodymium-132m2| style="text-indent:1em" | 132m2Pr| colspan="3" style="text-indent:2em" | 250(30)# keV| 2.46(4) μs| IT| 132Pr| (8+)||-id=Praseodymium-132m3| style="text-indent:1em" | 132m3Pr| colspan="3" style="text-indent:2em" | 300(30)# keV| 486(70) ns| IT| 132Pr| (8−)||-id=Praseodymium-133| 133Pr| style="text-align:right" | 59| style="text-align:right" | 74| 132.916331(13)| 6.5(3) min| β+| 133Ce| 5/2+||-id=Praseodymium-133m| style="text-indent:1em" | 133mPr| colspan="3" style="text-indent:2em" | 192.12(14) keV| 1.1(2) μs| IT| 133Pr| (11/2−)||-id=Praseodymium-134| 134Pr| style="text-align:right" | 59| style="text-align:right" | 75| 133.915697(22)| 17(2) min| β+| 134Ce| 2−||-id=Praseodymium-134m| style="text-indent:1em" | 134mPr| colspan="3" style="text-indent:2em" | 67.7(4) keV| ~11 min| β+| 134Ce| 6−||-id=Praseodymium-135| 135Pr| style="text-align:right" | 59| style="text-align:right" | 76| 134.913112(13)| 24(1) min| β+| 135Ce| 3/2+||-id=Praseodymium-135m| style="text-indent:1em" | 135mPr| colspan="3" style="text-indent:2em" | 358.06(6) keV| 105(10) μs| IT| 135Pr| (11/2−)||-id=Praseodymium-136| 136Pr| style="text-align:right" | 59| style="text-align:right" | 77| 135.912677(12)| 13.1(1) min| β+| 136Ce| 2+||-id=Praseodymium-137| 137Pr| style="text-align:right" | 59| style="text-align:right" | 78| 136.9106792(87)| 1.28(3) h| β+| 137Ce| 5/2+||-id=Praseodymium-137m| style="text-indent:1em" | 137mPr| colspan="3" style="text-indent:2em" | 561.22(23) keV| 2.66(7) μs| IT| 137Pr| 11/2−||-id=Praseodymium-138| 138Pr| style="text-align:right" | 59| style="text-align:right" | 79| 137.910757(11)| 1.45(5) min| β+| 138Ce| 1+||-id=Praseodymium-138m| style="text-indent:1em" | 138mPr| colspan="3" style="text-indent:2em" | 350(19) keV| 2.12(4) h| β+| 138Ce| 7−||-id=Praseodymium-139| 139Pr| style="text-align:right" | 59| style="text-align:right" | 80| 138.9089327(39)| 4.41(4) h| β+| 139Ce| 5/2+||-id=Praseodymium-140| rowspan=2|140Pr| rowspan=2 style="text-align:right" | 59| rowspan=2 style="text-align:right" | 81| rowspan=2|139.9090856(66)| rowspan=2|3.39(1) min| EC (51.3%)| rowspan=2|140Ce| rowspan=2|1+| rowspan=2||-| β+ (48.7%)|-id=Praseodymium-140m1| style="text-indent:1em" | 140m1Pr| colspan="3" style="text-indent:2em" | 127.8(3) keV| 0.35(2) μs| IT| 140Pr| 5+||-id=Praseodymium-140m2| style="text-indent:1em" | 140m2Pr| colspan="3" style="text-indent:2em" | 763.7(5) keV| 3.05(20) μs| IT| 140Pr| (7)−||-id=Praseodymium-141| 141Pr[2] | style="text-align:right" | 59| style="text-align:right" | 82| 140.9076596(16)| colspan=3 align=center|Stable| 5/2+| 1.0000|-id=Praseodymium-142| rowspan=2|142Pr| rowspan=2 style="text-align:right" | 59| rowspan=2 style="text-align:right" | 83| rowspan=2|141.9100516(16)| rowspan=2|19.12(4) h| β− (99.98%)| 142Nd| rowspan=2|2−| rowspan=2||-| EC (0.0164%)| 142Ce|-id=Praseodymium-142m| style="text-indent:1em" | 142mPr| colspan="3" style="text-indent:2em" | 3.694(3) keV| 14.6(5) min| IT| 142Pr| 5−||-id=Praseodymium-143| 143Pr| style="text-align:right" | 59| style="text-align:right" | 84| 142.9108226(19)| 13.57(2) d| β−| 143Nd| 7/2+||-id=Praseodymium-144| 144Pr| style="text-align:right" | 59| style="text-align:right" | 85| 143.9133107(29)| 17.28(5) min| β−| 144Nd| 0−||-id=Praseodymium-144m| rowspan=2 style="text-indent:1em" | 144mPr| rowspan=2 colspan="3" style="text-indent:2em" | 59.03(3) keV| rowspan=2|7.2(3) min| IT (~99.93%)| 144Pr| rowspan=2|3−| rowspan=2||-| β− (~0.07%)| 144Nd|-id=Praseodymium-145| 145Pr| style="text-align:right" | 59| style="text-align:right" | 86| 144.9145180(77)| 5.984(10) h| β−| 145Nd| 7/2+||-id=Praseodymium-146| 146Pr| style="text-align:right" | 59| style="text-align:right" | 87| 145.917688(37)| 24.09(10) min| β−| 146Nd| (2−)||-id=Praseodymium-147| 147Pr| style="text-align:right" | 59| style="text-align:right" | 88| 146.919007(17)| 13.39(4) min| β−| 147Nd| 3/2+||-id=Praseodymium-148| 148Pr| style="text-align:right" | 59| style="text-align:right" | 89| 147.922130(16)| 2.29(2) min| β−| 148Nd| 1−||-id=Praseodymium-148m| rowspan=2 style="text-indent:1em" | 148mPr| rowspan=2 colspan="3" style="text-indent:2em" | 76.80(20) keV| rowspan=2|2.01(7) min| β− (64%)| 148Nd| rowspan=2|(4)| rowspan=2||-| IT (36%)| 148Pr|-id=Praseodymium-149| 149Pr| style="text-align:right" | 59| style="text-align:right" | 90| 148.923736(11)| 2.26(7) min| β−| 149Nd| (5/2+)||-id=Praseodymium-150| 150Pr| style="text-align:right" | 59| style="text-align:right" | 91| 149.9266764(97)| 6.19(16) s| β−| 150Nd| 1−||-id=Praseodymium-151| 151Pr| style="text-align:right" | 59| style="text-align:right" | 92| 150.928309(13)| 18.90(7) s| β−| 151Nd| (3/2−)||-id=Praseodymium-151m| style="text-indent:1em" | 151mPr| colspan="3" style="text-indent:2em" | 35.10(10) keV| 50(8) μs| IT| 151Pr| (7/2+)||-id=Praseodymium-152| 152Pr| style="text-align:right" | 59| style="text-align:right" | 93| 151.931553(20)| 3.57(11) s| β−| 152Nd| 4+||-id=Praseodymium-152m| style="text-indent:1em" | 152mPr| colspan="3" style="text-indent:2em" | 115.1(3) keV| 4.16(10) μs| IT| 152Pr| (1+)||-id=Praseodymium-153| 153Pr| style="text-align:right" | 59| style="text-align:right" | 94| 152.933904(13)| 4.28(11) s| β−| 153Nd| 3/2−#||-id=Praseodymium-154| 154Pr| style="text-align:right" | 59| style="text-align:right" | 95| 153.93789(11)| 2.30(9) s| β−| 154Nd| (3+)||-id=Praseodymium-155| 155Pr| style="text-align:right" | 59| style="text-align:right" | 96| 154.940509(18)| 1.47(3) s| β−| 155Nd| 3/2−#||-id=Praseodymium-156| 156Pr| style="text-align:right" | 59| style="text-align:right" | 97| 155.9447669(11)| 444(6) ms| β−| 156Nd| 1+#||-id=Praseodymium-157| 157Pr| style="text-align:right" | 59| style="text-align:right" | 98| 156.9480031(34)| 307(21) ms| β−| 157Nd| 3/2−#||-id=Praseodymium-158| 158Pr| style="text-align:right" | 59| style="text-align:right" | 99| 157.95260(32)#| 181(14) ms| β−| 158Nd| 5−#||-id=Praseodymium-159| 159Pr| style="text-align:right" | 59| style="text-align:right" | 100| 158.95623(43)#| 134(43) ms| β−| 159Nd| 3/2−#||-id=Praseodymium-160| 160Pr| style="text-align:right" | 59| style="text-align:right" | 101| 159.96114(43)#| 170(140) ms| β−| 160Nd| 1+#||-id=Praseodymium-161| 161Pr| style="text-align:right" | 59| style="text-align:right" | 102| 160.96512(54)#| 90# ms
[>550 ns]| | | 3/2−#|